This invention relates in general to hinges for stabilizing the human knee and in particular to stabilizing knee hinges which simulate the movement of the human knee and which can be utilized to restrict the range of motion of the knee to any desired range or to completely immobilize the knee joint.
Knee joint braces and hinges are well known in the prior art. Such devices are typically utilized for treating fractures, re-education therapy of arthrolysis, orthopedic treatment of limbs after surgical correction, early re-education therapy of ligamentous lesions and to provide restraining articulated orthoses for traumatic knee lesions and other athletic knee injuries.
Generally, the splint or brace which utilizes a knee stabilizing hinge is constructed utilizing two identical side members each of which includes a femoral and tibial section, which are then fastened to the leg by means of straps or alternatively, fastened to a plaster or fiberglass cast.
The difficulty associated with the design of a stabilizing knee hinge is due to the complexity of the knee joint. Unlike the simpler hinge joints of the body, the knee joint has an axis of rotation which moves over a curve that is well defined and difficult to implement in a mechanical hinge. Recently, the manufacturers of such devices have begun to manufacture a so-called "polycentric" hinge which attempts to duplicate the motion of the knee utilizing gear and mechanically coupled dual pivots.
While representing an advance over the prior art, theses hinges have several shortcomings. Typically these hinges are too flexible to prevent hyperextension of the knee joint or too rigid to permit therapy. Additionally, the desirable aspect of restricting the range of motion of the knee utilizing a geared hinge is quite difficult. Several examples of knee hinges are known in the prior art. U.S. Pat. No. 4,340,041, issued to F. Frank, discloses an articulated knee splint which includes two anchor bars which may be locked, by means of a lock plate, into a desired angular position.
U.S. Pat. No. 4,337,764 discloses a knee joint brace which incorporates a "polycentric" hinge which includes an arcuate groove with two adjustable stop pins to permit a variation in the amount of flexion permitted. A second hinge below the adjustable hinge is utilized to simulate the motion of the human knee.
U.S. Pat. No. 4,088,130, issued to L.T. Applegate, discloses a simple lockable hinge which may be utilized to restrict the range of motion of the knee to a desired arc; however, there is no provision in Applegate to simulate the complex motion of the human knee.
U.S. Pat. No. 3,826,251 discloses a knee hinge that utilizes two slots to simulate the knee motion. A straight vertical slot and an arcuate slot are provided to demonstrate the pivot and slide motion of the knee. The arcuate slot includes a detent to permit the leg to be locked in the rigid position for prolonged standing.
Finally, U.S. Pat. No. 3,779,654 discloses an artificial knee joint which utilizes two arcuate cam surfaces to simulate the natural knee motion. There is no provision in this joint however for the restriction of the range motion of the knee.